Circular orifice plate fluid flow meters and flow conditioning plates are traditionally designed with a diameter that is compatible with the size and dimension of the specific pipe coupling flanges between which the orifice plate will be installed. Standard ANSI, DIN and JIS pipe flanges are designed with a variety of pressure ratings. For example ANSI standard flanges are classified as 150, 300, 600, 900, 1500 and 2500. For each of these ratings the flanges will have different dimensions and different number of bolt holes as well as different spacing and size of the holes comprising the bolt hole circle. Accordingly, for a given pipe line size, prior art orifice plates have had to be sized to fit the particular pressure rated flange pair being used in the application.
The requirement for centering an orifice plate so that its center is coaxial with the longitudinal center line of the pipes carrying the attachment flanges is well known. It is also acknowledged that visually performed alignment of a flow meter within its compressive mounting pipe flanges is time consuming and unreliable. Various alignment and centering devices have been proposed, including various gauges and installing tools. Such attempts are represented by U.S. Pat. No. 4,345,464 for Centering Device for Flowmeters Interposed in Flow Line and U.S. Pat. No. 5,632,632 for Flowmeter Alignment Device. The '464 patent discloses a pair of rectangular plates acting as camming devices that take advantage of the normal play present in a bolted pipe flange arrangement, The '632 patent discloses both a closed ring and an arc that are designed to mate with an edge of the raised face of a pipe flange. While adequate for a single pipe size and a single pressure rated pipe flange and flow meter, one of these devices of the prior art is not adapted for use with a large number of different pipe flanges.
It is therefore the primary object of the present invention to provide a selection of arcuate appliances that center and permanently support a single size of orifice plate within any one of a plurality of different pressure rated flange pairs that interconnect pipes of the same size.